Continued Advances in Performance in Geothermal Operations at FORGE Through Limiter-Redesign Drilling Practices

Abstract

Abstract The continued application of physics-based limiter redesign workflow in the hard geothermal granite at the Utah FORGE project resulted in additional advances in hard rock practices and performance. The physics-based approach provided an effective framework to mitigate and address drill bit, geologic, trajectory, and downhole tool challenges and limitations. The advances were possible because the operating team was trained to understand how bit dysfunction and other non-bit limiters physically work, and had the knowledge required to mitigate these limiters in real-time or redesign to extend them when possible. In the final runs of the most recent well in the field, the ROP when rotating bent motors ranged from 150 ft/hr. to more than 300 ft/hr. and overall cumulative on-bottom rotating hours were reduced despite a more challenging, high angle well path with steering constraints. The paper covers the workflows and practices used to: Extend the safe WOB and RPM limits of bits beyond the industry's common practices in granite (65-70K lbs. and 250 RPM on 9.5" bits) Continue to expand the industry's understanding of the application of clear water drilling fluids to mitigate low drill rates caused by dilatant strengthening (bottom hole balling) Drill with RSS in granite to achieve a smooth curve to 65° inclination. Demonstrate practices for drilling a high angle tangent with a bent motor to achieve higher drill rates while still delivering borehole quality equaling or exceeding that of an RSS. Evaluate practices to reduce the large decline in ROP observed in early footage with all bits in hard formations. This represents the largest opportunity for additional performance gains in geothermal drilling. The paper incorporates both the specific practices implemented and the processes required to take a new operations team from initial project startup to record setting performance within the span of a single well (each FORGE well has been drilled by a different team). The authors’ intent in this and the previous paper, SPE 208798 (Dupriest and Noynaert, 2022), is to enable others to duplicate the gains at FORGE.